The invention relates to an implant, a bone implant, which contains an implant as per the invention and a set for production of an implant and their uses. Furthermore, the invention describes a method of making an implant as per the invention.
There has long since been a need in orthopedics and surgery to fill in bone defects again after fractures, or an amputation as a result of tumor diseases or inflammation, with bone material or a replacement that is similar to bone. CN 102085123 A discloses a dual-component implant in connection with this that consists of a non-woven titanium wedge-wire cylinder that is filled in with a bone replacement material in an interlocking way. The bone replacement material consists of a course-grained calcium phosphate cement constituting 40 to 94% of the mass by weight and a binding material constituting 5 to 29% of the mass by weight. The two cylinder heads of the non-woven titanium wire cylinder are closed up with biodegradable casing caps; the natural bone tissue can grow from the cylinder ends into the implant because of that. The non-woven titanium wedge-wire cylinder is consequently not included in the bone replacement material, but instead only serves as a filling container.
Materials with high mechanical stress-bearing capacities are required for the implantation, especially implantation in bone. The addition of a mesh structure to polymethyl methacrylate cements to improve their mechanical characteristics is a known procedure. U.S. Pat. No. 4,064,567 discloses a joining system between bone and an implant for this that includes a mesh structure made, for instance, of non-resorbing metals, plastic or carbon or resorbable fibers such as Dacron. The mesh structure is filled with a polymethyl methacrylate cement and is intended to serve in improving the fixation of prostheses and, among other things, avoiding fracture points.
Moreover, the aim is to use materials in implants that promote the ingrowth of the natural bone tissue (that are therefore bioactive) and that are successively eliminated in the body (that are therefore resorbable), in order to avoid a later removal of an implant. Mineral bone cements, for instance based on calcium phosphates, are commonly used as bioactive and resorbable materials. It is possible to create mineral bone cements with high compressive strength, but implants made of a pure mineral bone cement can only be subjected to a very low level of bending stress.
The reinforcement of mineral bone cements with resorbable polymer fibers to improve the mechanical characteristics of implants based on mineral bone cements is a known procedure. The mechanical characteristics of the implants based on mineral bone elements can be improved because of that, but the compressive strengths and bending strengths are still inadequate.
U.S. Pat. No. 6,955,716 B2 discloses a calcium phosphate bone replacement material here that constitutes more than 20% of the mass by weight of non-metallic, resorbable fibers. The non-metallic, resorbable fibers are mainly selected from polymer fibers, for instance Vicryl threads, polyglactin 910, Ethicon, Somerville, N.J.; Panacryl™ threads, Ethicon, N.J.; or ceramic silicon carbide fibers.
Filling resorbable, mineral bone cement into open-cell metal structures such as foams or hollow-sphere structure made of metal to improve the mechanical characteristics of implants based on mineral bone cements is a known procedure. A bone implant of that type is disclosed in WO 2008/064672; a resorbable mineral bone cement based on calcium phosphates and/or magnesium phosphates is filled into a metallic foam or a metallic hollow-sphere structure in an at least a partially interlocking way. Metallic structures are chosen for this whose rigidity is in the range of healthy, cortical human bone. High compressive strength of the implant is already made possible at the point in time of the implantation because of the metallic structure. Bone tissue successively grows into the implant because of the resorbability of the mineral bone cementer; the remaining metal with rigidity comparable to that of healthy bone remains. A drawback of the metal foams or metal hollow-sphere structures that are used is that the mechanical characteristics can only be adjusted in a limited way. A targeted adjustment of mechanical characteristics is not possible; rather, these metal structures have the same stress characteristics when there is stress from any arbitrary direction.
WO 2011/157758 A2 discloses a bone implant that consists of a resorbable material containing magnesium with a corrosion-resistant coating made of magnesium ammonium phosphate and a mineral bone cement. The material containing magnesium can be in the form of a centrally placed wire and/or diffusely distributed chips.
There is therefore a need to provide implants with adjustable stress characteristics that have, in particular, high bending strength and high compressive strength.